1. Field of the Invention
The present invention relates to ladders useable as lifesaving equipment for operators who fall into water by accident, which ladders are mounted on quays of harbors, coasts, rivers, etc. and on wall surfaces of sea banks, and more specifically, to a life ladder also serving as a fender for preventing boats from being damaged when the boats come in contact with the quay.
Recently, many wall surfaces of quays of harbors or sea banks of coasts or rivers have an upright construction and one disadvantage of such constructions is that if a person should fall into the water by accident, he would not be able to climb along the wall surface to escape from the water. It is therefore necessary to arrange a number of ladders at suitable intervals along the wall surfaces as described above.
Such ladders are widely employed and are made of metal materials such as iron and stainless steel, are applied with rubber lining to a part of such metal ladders for rust-proofing, or are made of a rust-resisting hard synthetic resin material.
However, where these life ladders are installed on the wall surfaces of quays at and from which boats arrive and depart, sometimes the boat hulls come into contact with the ladders and damage the ladders. Further, when a small boat comes along side the quay which is high in height from the water level to the upper surface of the quay, these ladders are used to transport people up and down between the boat and the quay. In this case, the ladders are sometimes broken due to shocks produced when the boat comes into contact with the bank or due to the up and down movement of the boat during mooring.
2. Description of Prior Art
In view of the foregoing, an attempt has been made to construct a life ladder which also functions as a fender so that the kinetic energy which exists when the boat comes into contact with the bank is absorbed by said life ladder. Such a fender and life ladder combination is proposed, for example, in Japanese Patent Laid-open No. 55-19383, the arrangement of which is explained by reference to FIG. 6. This fender and life ladder combination comprises a pair of hollow square posts 11 and 12 made of rubber vertically mounted on the wall surface of quays or the like and a plurality of rubber step members 13 extending between opposed surfaces of said posts 11 and 12. The rubber posts 11 and 12 accommodate therein metal chains 14 and the rubber step members 13 also accommodate therein metal chains 15. The metal chain 15 has both ends connected to the metal chain 14. However, the aforesaid fender and life ladder is wholly larger in size than prior art iron ladders, and requires extremely complicated steps in molding and processing, such as the step of molding of the rubber posts 11, 12, the time-consuming step of forming the rubber step members 13 integral with said posts, and the time-consuming step of accommodating the chains 14, 15 in said posts 11, 12 and said step members 13. In addition, it requires a large and complicated molding device to manufacture ladders, and therefore, the price required per ladder inevitably becomes high.
On the other hand, the distance which an operator who has fallen into the sea while fully clothed may swim is usually said to be about 30 meters during a severe cold season, and in order to achieve a saving function under such a limit condition, it is desirable to install life ladders on the wall surfaces of quays or the like at intervals as short as possible. However, since prior art rubber ladders are high in unit price, as a practical matter the optimum condition of installation is not fulfilled.
One example of a fender which protects the hull from shocks when the boat comes into contact with the bank is shown in British Pat. No. 945,456, for example, which discloses a fender composed of a rubber cylindrical body whose cross section is trapezoidal, which comprises an abutment portion in abutment with the wall surface of the quay or the like, a buffer portion arranged in position opposed to said abutment surface and with which the hull or the like directly contacts, and two side wall portions which are equal in length to each other for connecting the ends of said abutment portion and buffer portion. Also, U.S. Pat. No. 4,267,792 discloses an elongated fender integrally formed of a resilient material and having an inverted Y-shaped cross section, comprising a shock receiving portion having a substantially rectangular cross section having one flat shock receiving surface with which the hull directly contacts, a pair of side walls with open legs which extend symmetrically to the left and right in directions opposed to each other from said shock receiving portion, and a pair of mounting portions extending horizontally and outwardly from the respective lower ends of said side wall portions. These fenders have great compression deformation and buckling deformation, are excellent in shock absorbing characteristics and are simple in construction, and therefore have a tendency for wise use.
Therefore, the present invention comprises an improvement upon these conventional fenders and provides a fender and life ladder using the general principles of these conventional fenders.